A method for measuring in situ oxygen consumption rates of freshwater gastropods

In situ oxygen consumption rates can be used to evaluate respiratory costs of organisms in the natural environment. We determined the in situ oxygen consumption rates of freshwater gastropods by using an assay of the coenzymes involved in the electron transport system (ETS). This assay may be used to estimate in situ and in vitro metabolic rates of individuals when direct monitoring of oxygen consumption is not practical. The relationship between ETS activity and measured oxygen consumption was determined for individuals of 3 common Lake Michigan snail species: Elimia livescens, Stagnicola woodruffi, and Physella integra. The snails were exposed to various temperature conditions to stimulate a wide range of oxygen consumption. After 14 of acclimation to the experimental conditions, oxygen consumption rates were measured daily. After 5 d, the snail tissue was removed from the shells, flash, frozen, and stored in liquid nitrogen until the ETS assay could be performed. Oxygen consumption was highly correlated with ETS activity for all 3 species (p < 0.001). The in situ oxygen consumption rates of these snails can be evaluated using the calibration of oxygen consumption to ETS activity.